Simon, it’s not uncommon that when you use Mosaic/Tidal, music is streamed from a different Global cache provider than when you use Tidal’s native PC/Mac App by itself. So, the former could fail, while the latter seems to work just fine.
In which case the problem is within your Internet Service Provider’s domain, rather than inside your house or your dCS Network Bridge as such.
Have a read of the following post and maybe try the suggested diagnosis, it might lead to additional insights into the problem you’re facing;